Vehicle braking systems often include a brake control assembly to provide anti-lock-braking (ABS) functionality which utilizes a brake fluid accumulator assembly of a brake control assembly, wherein the brake control assembly sometimes is called a hydraulic control unit or HCU.
A conventional brake fluid accumulator assembly is a passive pump-inlet (release) accumulator having a piston and spring mechanization which relies on the pressure volume relationship (high pressure, low volume transitioned into low pressure, high volume) to relieve excess brake pressure from the wheel brake to avoid wheel lockup during braking. The minimum release pressure at the wheel brake is limited by the accumulator preload and the piston seal drag. The accumulator preload, provided by the compressed spring during assembly, is necessary to ensure a minimum inlet pressure to the non-self-priming controllable pump to ensure pump-out (emptying) of the accumulator and to ensure that the piston overcomes seal forces to return to its home position. Seal drag results from the “standard” needs of the dynamic seal interface between the bore and the piston.
A conventional brake control assembly having a brake fluid accumulator assembly typically includes check valves and various controllable valves. A controllable pump and the controllable valves are operatively connected to an electronic control unit. The electronic control unit receives inputs from wheel speed sensors and/or other system inputs to control the controllable pump and the controllable valve to prevent wheel lockup during brake apply by the driver, as is known to those skilled in the art.
What is needed is an improved brake control assembly having a brake fluid accumulator assembly.